1. Field of the Invention
The present invention relates to lens systems and particularly to lens systems suited for use in super wide-angle applications where the field angle is in excess of 90 degrees or 100 degrees. These lens systems are especially suitable for use in exposing film or other sensitive media in panoramic cameras.
2. Description of the Prior Art
Known super wide-angle lens designs utilize strong negative front lens groups that are followed by a stop and then an even stronger positive lens group to re-establish the effective focal length. Such designs are disclosed in U.S. Pat. Nos. 4,525,038; 4,431,273; 4,412,726; 4,381,888; and 3,045,547. The net result of this arrangement is an inverted telephoto effect (i.e. the back focus of the lens system is longer than the focal length). In addition, an exit pupil distance in this type of lens system is long enough to reduce the angle at which the principal ray strikes the image plane thus reducing the relative illumination fall-off due to cosine fourth effect. However, such lens systems tend to have lens elements with large diameters, many lens elements and high manufacturing costs.
Accordingly, it is the principal object of the present invention to provide an improved lens system having a wide angle side-to-side coverage, few lens components, smaller lens element diameters and reduced manufacturing costs.
It is another object of this invention to provide a lens system for consumer camera application that achieves good aberration control with only a few and preferably only two lens components.